Conventional shelters for protection against various weather-related elements, such as sun, rain, wind, snow, etc. may come in a variety of shapes, sizes, and have varying degrees of complexity related to the assembly or disassembly of the shelter. By way of example, U.S. Pat. No. 4,355,650 to Beaudry describes a conventional shelter that takes the form of a portable and collapsible shelter having a plurality of support ribs or bows which are pivotally mounted to a hub at each end thereof. Each rib is made up of at least three completely separable pieces. The fabric covering of the structure provides compressive forces to the bows to maintain the assembled condition of the bows.
When erected, the structure is maintained in an open position by a pair of side braces positioned at the vertical sides of the structure. A first side brace is pivotally attached to the rib which rests on the ground; a second brace is pivotally attached to the rib forming the entrance to the structure. The braces are pivotally attached to each other at their other ends by a rivet. A keyhole slot is provided in the center rib for purposes of receiving the head of the rivet attaching the two braces to each other. The large portion of the keyhole slot is positioned closest to the hub while the smaller elongated portion of the slot extends away from the hub. When the ribs or bows are fully fanned out, the head of the aforementioned rivet fits within the elongated portion of the keyhole slot and the braces form an angle with each other with the apex of the angle extending away from the hub.
The outer covering of the shelter is then snap fastened to the first and last bows. The resulting tautness of the outer covering provides a force which tends to cause the bows to collapse. Such force, however, in conjunction with the angle formed by the braces, firmly locks the rivet head within the elongated portion of the keyhole slot and thereby prevents the structure from collapsing.
A combination digging tool and anchor prevents the structure from being moved by the wind when erected. A tie rod is pivotally attached to each hub and extends therefrom into the ground. A small trench is dug into the ground at the location of the hub with the aid of the combination tool. When an appropriate depth is achieved, the tool is engaged with the tie rod, forming an inverted “T” within the trench. The trench is then backfilled with earth or sand which buries the anchor within the covered over trench.
During assembly, the bows are connected to form five “U”-shaped bows. Next, the bows are fully fanned out by applying a force to the pinned braces in a direction away from the hub. The inherent collapsing action of the bows together with the angle formed by the braces causes a connection rivet to maintain its position at the end of a keyhole slot, which end is furthermost away from the hub. At this point of the erection sequence of shelter, the fabric covering is draped over the framework of shelter and then snap fitted to one or more bows. The interrelating forces of the bows, the fabric covering, and the braces as they act and react with each other maintains the shelter in a fully erected position.
U.S. Pat. No. 7,178,540 to Eder describes an improved hub for a personal shelter or canopy. The hub includes a number of spherical rotating joint elements captured in a hub body. The joint elements provide rotational movement of canopy frame elements to allow easy opening and collapsing of a canopy frame and cover. Two canopy hubs are preferably connected along a common axis by a rigid cross bar. Each hub may be formed by molding in high-density plastic and combined with stub arms to facilitate subsequent assembly of a completed canopy.